Monte Carlo Study Using GEANT4 of Cyberknife Stereotactic Radiosurgery System / 의학물리

Cyberknife with small field size is more difficult and complex for dosimetry compared with conventional radiotherapy due to electronic disequilibrium, steep dose gradients and spectrum change of photons and electrons. The purpose of this study demonstrate the usefulness of Geant4 as verification tool of measurement dose for delivering accurate dose by comparing measurement data using the diode detector with results by Geant4 simulation. The development of Monte Carlo Model for Cyberknife was done through the two-step process. In the first step, the treatment head was simulated and Bremsstrahlung spectrum was calculated. Secondly, percent depth dose (PDD) was calculated for six cones with different size, i.e., 5 mm, 10 mm, 20 mm, 30 mm, 50 mm and 60 mm in the model of water phantom. The relative output factor was calculated about 12 fields from 5 mm to 60 mm and then it compared with measurement data by the diode detector. The beam profiles and depth profiles were calculated about different six cones and about each depth of 1.5 cm, 10 cm and 20 cm, respectively. The results about PDD were shown the error the less than 2% which means acceptable in clinical setting. For comparison of relative output factors, the difference was less than 3% in the cones lager than 7.5 mm. However, there was the difference of 6.91% in the 5 mm cone. Although beam profiles were shown the difference less than 2% in the cones larger than 20 mm, there was the error less than 3.5% in the cones smaller than 20 mm. From results, we could demonstrate the usefulness of Geant4 as dose verification tool.

A Study on the Methylation of p 16 Gene Promotor in the Uterine Cervical Neoplasia / 대한산부인과학회잡지

No abstract available.

Prenatal Cytogenetic Diagnosis in Balanced Chromosome Translocation Carriers / 대한산부인과학회잡지

Retrospective analysis of chromosomal abnormalities was performed on 75 couples who had recurrent spontaneous abortion. Karyotyping of their peripheral blood lymphocytes was made on 75 patients and 75 their husbands. The overall incidence of chromosomal aberrations was 22.7 %(17 in 75 couple). Number of chromosomal abnormalities in wives was twelve. Another chromosomal abnormalities were found in five husbands. All of them were balanced form and their phenotypes were normal. The incidence of translocations among total chromosomal abnormalities was 64.7 % (11/17). The incidence of reciprocal translocation(72.7 %) was higher than that of Robertsonian translocation (27.3 %). There were six other abnormalities including one case of inversion and five cases of polymorphisms. amniocentesis or chorionic villi sampling was performed during subsequent pregnancy to couples who had balanced chromosomal abnormalities. The karyotypes were classified as balanced translocation in seven cases, inversion in one case and normal karyotype in one case. This study suggests that prenatal diagnosis should be emphasized in couples in which one person is the carrier of a balanced chromosomal abnormality.

A Clinical Study for Oxytocin use of Labor Induction / 대한주산의학회잡지

OBJECTIVE: The objective of this study is to compare the effectiveness and safety in the labor induction between the high dose oxytocin method and the new low dose oxytocin method. STUDY DESIGN: Firstly, we selected 125 pregnant women hospitalized, having the indication of labor induction from March, 1995 to August, 1996. Of them, we selected 61 pregnant women tothem the high dose oxytocin method was used, as the control group, and in- creased the quantity of 2.5 mU/min every 20 minutes with the start dose of 2.5 mU/min to them. On the other hand, with the start dose of 1.25 mU/min, we increased the quantity of 1.25 mU/min every 20 minutes to the study group of low dose oxytocin method, 64 pregnant women. RESULTS: No statistical significance was found in the time from the effective uterine contraction to the delivery in the study group, in contrast to that of the control group to them the labor induction was conducted by using the high dose oxytocin. Maximum amount used to the high dose oxytocin was significantly more than that of the low dose oxytacin, but in the total given dose, there was no significant difference between two groups. Maxi- mum uterine contraction of the control group did not show any significant. difference from that of the study group, and there was also no significant difference in the frequency of generating the complications such as fetal distress. CONCLUSION: There was no difference in the labor.induction -to delivery time, and the complications of fetus, between the existing high dose oxytocin method and the new low dose oxytocin method. Therefore it is thought the low dose oxytocin method may reduce the possibility of a complieation compared with the high dose oxytocin method. However, it is considered this matter must be investigated further in the futrre.